Thermostatic device having augmenting bimetallic coiled sections



y 1955 c. A. THURMOND 3,197,591

THERMOSTATIC DEVICE HAVING AUGMENTING BIMETALLIC COILED SECTIONS Filed D60. 28, 1961 2 Sheets-Sheet l Charles A. Thurmond INVENTOR.

y 1965 c. A. THURMOND 3,197,591

THERMOSTATIC DEVICE HAVING AUGMENTING BIMETALLIC COILED SECTIONS Fil e 2 1961 2 Sheets-Sheet 2 Fig.9

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Char/es A. Thu/mono INVENTOR.

United States Patent 3,197,5s1 THERMOSTATIC DEVICE HAVING AUGMENTING BIMETALLIC COILED SECTIGNS Charles A. Thunnond, Asheville, NC. (Box 332, Oak Hill, Fla.) Filed Dec. 28, 1%1, Ser. No. 162,713 6 Claims. (Cl. 200-113) This invention relates to a new and useful thermostatic device and more particularly, to a thermally responsive switch device for use in a fire alarm system.

The novel feature of the present invention revolves about a bimetallic element which responds to predetermined increases in temperature to more dependably close electrical contacts for providing a fire alarm. It is therefore a primary object of the present invention, to provide a thermal responsive device, the response of which is more positive and dependable than any other similar device of comparable simplicity and cost.

Another object of this invention is to provide a thermally responsive device which embodies a novel bimetallic strip element through which electrical contact is effected with greater engagement pressure and with quicker response and yet capable of being more easily adjusted than any other heretofore known bimetallic strip element.

A further object of this invention is to provide a thermostatic device which is more dependable than comparable devices heretofore used because of a self-cleaning contact feature thereof.

An additional object of this invention is to provide a thermostatic device which in addition to being economical to manufacture, is installationally flexible.

In accordance with the foregoing objects, the thermostatic device of the present invention includes a bimetallic strip which is formed into two coil sections interconnected by a diametral connecting portion of the strip,

one of the coil sections being tangentially. connected to an anchoring portion through which the bimetallic strip is connected to one electrical terminal while the other coil section is tangentially connected to a movable contact portion, a remote end of which is adapted to engage a fixed contact surface. The coil sections are so arranged that changes in temperature will simultaneously cause one of the coil sections to uncoil while the other will be caused to coil. The uncoiling and coiling of the interconnected coil sections occurs in such directions as to augment each other and thereby displace the movable contact portion in a direction so as to engage the fixed contact surface with a surface-wiping movement so as to remove any collected dust or particles from the contact surfaces and assure a good positive electrical contact. Furthermore, the combined displacement of the coil sections together with the displacement effected by the anchoring portion and movable contact portion of the bimetallic strip in response to temperature changes accounts for the unexpectedly rapid response of the thermostatic device of the present invention.

These together with other object-s and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a perspective view of one form of installation for the novel thermostatic device of the present invention.

FIGURE 2 is a sectional view taken through a plane indicated by'section line 22 in FIGURE 1.

FIGURE 3 is a sectional view taken through a plane indicated by section line 3-3 in FIGURE 2.

FIGURE 4 is a partial sectional view taken through a plane indicated by section line 4-4 in FIGURE 2.

3,197,591 Patented July 27, 1965 FIGURE 5 is a perspective view of the bimetallic ele ment of the present invention.

FIGURE 6 is a circuit diagram of an alarm system associated with the thermostatic device of the present invention.

FIGURE 7 is a perspective view of another form of installation for the thermostatic device of the present invention.

FIGURE 8 is a longitudinal sectional view through the device illustrated in FIGURE 7.

FIGURE 9 is a partial sectional view taken substantially through a plane indicated by section line 99 of FIGURE 8.

FIGURE 10 is a circuit diagram illustrating a typical installational system for thermostatic devices of the present invention.

Referring now to the drawings in detail, it will be observed in FIGURE 1, that the thermostatic device generally referred to by reference numeral 10 may be mounted at any desired location for the purpose of responding to an increase in temperature beyond a certain value so as to indicate the presence of fire and thereby render an alarm signal at some remote location. Referring for example to FIGURE 6, a typical alarm system installation is illustrated wherein the thermostatic device It is electrically connected to a remote source of electrical power 12 in series with a remotely located alarm indicating device 14. Also connected in parallel with the device 14 may be an additional indicating device 16 and an alarm device such as buzzer 18. Upon closing of the circuit by the thermostatic device 10, an alarm signal may therefore be provided at some remote location by the indicator 14 While closer identifying alarm devices 16 and 18 would be simultaneously operated.

Referring now to FIGURES 2, 3, 4 and 5 in particular, it will be observed that the device 10 is housed within a typical push button type of casing 20 from which the push button switch has been removed exposing the opening 22. The opening 22 is therefore closed by a screen element 24 to protect the thermostatic element mounted within the casing 20 and yet exposing the elements there within to heat. The casing is therefore provided with apertures 26 providing sufiicient ventilation therethrough so that the device will properly respond to any dangerous increase in temperature as desired. Mounted within the casing 20 is a base member 28 made of nonconductive material and supporting in spaced relation to each other terminal rivets 30 and 32. The terminal rivet 30 forms a fixed contact surface 34 on the head thereof while the shank of the rivet exposed on the other side of the base 28, is welded to a lead 36 from an electrical connecting cable 38. The other lead 40 from cable 38 is Welded to the split shank end 42 of the rivet 32 which extends through an aperture in the .base 28 within which an end tab portion 44 of a thermally responsive coil device generally referred to by reference numeral 46 is anchored. As more clearly seen in FIGURE 5, the coil device 46 is formed from a single bimetallic strip and includes a first J-shaped section consisting of an anchoring portion 48 connected to the anchoring tab 44 at one end and tangentially connected at its other end to a forward coil portion 50. The forward coil portion is connected to a reverse coil portion 52 through a diametral connecting portion 54 for simultaneous coiling and uncoiling with respect to movable coil centers disposed between the coil portions 50 and 52. Tangentially connected to the reverse coil portion 52 is a movable contact portion 56 forming therewith a second J-shaped section disposed in inverse relation to the first section. The upturned end 58 of contact portion 56 forms a movable contact 60 for engagement with the fixed c'on tact surface 34 on the rivet 30. The thermostatic coil element 46 is thereby arranged so that the forward coil 50 answer will uncoil in response to increases in the ambient air temperature while the reverse coil portion 52 will simultaneously coil in response to increases in temperature. As a result thereof, the forward coil section 50 will cause angular displacement of the reverse coil section 52 in the same general direction with respect to the coiling of the section 52 so as to impart a combined displacement to the movable contact portion 56 for more rapid and positive engagement of the contact portion 60 with the contact surface 34. Furthermore, the thermal displacement of the portions 48 and 56 in themselves will produce a combined linear wiping displacement when being angularly displaced by the coil sections 50 and 52. In accordance with this operation, the higher expanding metal of the bimetallic strip forming the coil element 46 will be disposed on the radially inner side of the forward coil section '0 while the higher expanding metal will be on the radially outer side of the reverse coil section 52 by virtue of the interconnection of the coil sections by the diametral portion 54, which diametral portion 54 also transmits the linear and angular displacements of the anchoring portion 48 and the coil section 50 to the coil section 52. The contact point 60 is therefore displaced in such a direction in response to an increase in temperature, as to not only engage the fixed contact surface 34 with a more positive pressure but also moves relative to the surface 34 in a direction to wipe the surface and thereby remove dust and other particles that may collect thereon. Accordingly, a more dependable and sensitive operation of the thermostatic device results despite prolonged disuse.

FIGURE illustrates another installational set-up for which the thermostatic device of the present invention is [also particularly useful, demonstrating its installational flexibility as hereinbe-fore mention. The devices 62. may therefore be placed in a plurality of separated areas such as hotel rooms, motel cabins, etc. Each of the devices 62 is therefore connected to a source of power 64 for operation of an associated alarm. The source of power is also connected in parallel to a plurality of remote locational identifying indicators 66 and buzzers 68 which are connected to the thermostatic devices 62. The indicating devices 66 and alarm devices 68 may therefore be mounted on a panel at one remote location so that a fire occurring in any one of the separated areas with which the plurality of thermostatic devices 62 are associated, may be identified and located in addition to providing a general warning. The devices 62 in addition to providing the fire alarm signal may also provide an alarm signal at the installational location thereof.

Referring now to FIGURES 7-9, it will be observed that the device 62 is enclosed within a buzzer-type housing 70 provided with a plurality of apertures 72 for ventiiation purposes as described with respect to the device 10 of FIGURES l4. The buzzer housing 70 therefore encloses a typical type of buzzer mechanism generally referred to by reference numeral 74 which is electrically connected to the fixed contact rivet 76 while the other electrical terminal of the buzzer device 74 is connected to the terminal post 78 to which leads from the power source 64- are connected. Mounted in fixedly spaced reilation to the fixed contact rivet 76 on a nonconductive base 8% is the anchoring rivet 82 to which a bimetallic coil strip 84 is anchored and operative in a manner similar to that described with respect to FIGURES 2-5. The rivets 76 and 82 are therefore respectively connected to the source of power 64 and the indicating and alarm devices 66 and 68 on the remotely located alarm panel as described with respect to FIGURE 10. The device 62 may therefore be mounted in any suitable location for detecting the presence of fire and providing the alarm both at the fire location and at some remote location.

From the foregoing description, operation and utility of the present invention will be apparent. It will therefore be appreciated, that the novel bimetallic thermal strip by Virtue of its unique design and operation enables the construction of an economical thermostatic device having unexpectedly rapid, positive and dependable operational attributes. In addition, the simplicity of the thermostatic device and the small size thereof endows it with the installational flexibility as hereinbefore demonstrated.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

l. A thermostatic alarm assembly comprising, anchor means, fixed contact means spaced from said anchor means and thermal deflecting coil means including a coil section operatively connected to the anchor means for uncoiling in response to an increase in the ambient temperature of its surrounding medium, a reversely coiled section responsive to an increase in the ambient, temperature of its surrounding medium for coiling simultaneously with said uncoiling of said coil section, means interconnecting said coil sections for simultaneous coiling and uncoiling with respect to movable coil centers disposed between said coil sections and movable contact means operatively connected to said reversely coiled section for displacement by the reversely coiled section in a contact pressure direction for positive contact engagement, and a contact wiping direction for surface cleaning of said fixed contact means.

2. The combination of claim 1, wherein said coil means is integrally formed from one bimetallic strip having a higher expanding metal on an inner radial side of one of said coil sections, the other of said coil sections having a lower expanding metal on the inner radial side thereof.

3. The combination of claim 2, wherein said movable contact means includes a thermally responsive member tangentially connected to said reversely coiled section defleeting in a direction to augment dispacement thereof by the coil sections.

4. A thermostatic alarm assembly comprising, anchor means, .fixed contact means spaced from said anchor means, and thermal deflecting coil means including a coil section operatively connected to the anchor means for uncoiling in response to increase in the ambient temperature of its surrounding medium, a reversely coiled section responsive to an increase in the ambient temperature of its surrounding medium for coiling simultaneously with said uncoiling of said coil section, means interconnecting said coil sections for simultaneous coiling and uncoiling with respect to coil centers disposed between said coil sections, and movable contact means operatively connected to said reversely coiled section for displacement by the reversely coiled section in a contact pressure direction for positive contact engagement and a contact wiping direction for surface cleaning of said fixed contact means, said movable contact means including a thermally responsive member tangentially connected to said reversely coiled section defleeting in a direction to augment displacement thereof by the coil sections, said anchor means including a thermally responsive segment tangentially connected at one end thereof to the coil section and at the other end fixedly anchored, said interconnecting means comprising a diametral portion extending through said coil centers, said coil means being integrally formed from one bimetallic strip having a higher expanding metal on an inner radial side of one of said coil sections, the other of said coil sections having a lower expanding metal on the inner radial side thereof.

5. In a thermostatic sensing device, a pair of fixedly spaced terminal elements, and a sensing element exposed to ambient temperature comprising an elongated -bi-.

metallic strip having opposite sides formed of metals with different thermal coefficients of expansion, said strip including a pair of sections having coil portions forming a generally circular configuration, a connecting portion enclosed Within said circular configuration interconnecting diametrically spaced ends of the coil portions, one of said sections including an anchor portion extending tangentially from the circular configuration and secured to one of the terminal elements, the other of said sections including a contact portion extending tangentially from the circular configuration in circumferentially spaced relation to the anchor portion for contact with the other of the terminal elements, the side of the strip along the coil portion of the other of said sections facing radially inward of said circular configuration and being formed of the metal having the lower thermal coefficient of expansion tending to angularly displace the contact portion relative to the connecting portion in response to ambient temperature variations, the side of the strip along the coil portion of said one of the sections facing radially inward of the circular configuration and being formed of the metal having the higher thermal coefficient of expansion tending to angularly displace the connecting portion in response to temperature variations augmenting displacement of the contact portion by the coil portion connected thereto.

6. In a thermostatic sensing device having an anchor element, a contact element fixedly spaced from said anchor element and a sensing element secured to the anchor element, said sensing element comprising movable coil means having radially inner and outer ends, contact means connected to the radially outer end of the movable 0 coil means for angular displacement relative to the Contact element, anchoring coil means having a radially inner end and a radially outer end, means connecting said radially outer end of the anchoring coil means to said anchor element for linear and angular displacement of the radially inner end relative to the contact element, and means interconnecting the radially inner ends of the coil means for simultaneous coiling and uncoiling of the respective coil means relative to each other in response to ambient temperature variations to augment said angular displacement of the contact means with contact wiping movement relative to the contact element.

References Cited by the Examiner UNITED STATES PATENTS 1,854,810 4/32 Sanborn 200138 1,972,975 9/34 Brady 200-138 2,063,705 12/36 Smulski 200-422 2,073,757 3/37 Schaefer 200l39 2,162,098 6/39 McCabe 200-138 2,162,524 6/39 Brace et a]. 200l38 2,308,091 1/43 McCullough 200139 2,508,700 5/50 Wilcox 200-138 2,671,837 3/54 Ray 200-438 2,764,649 9/56 Lehde 200113 3,050,601 8/62 Bohn 200138 BERNARD A. GILHEANY, Primary Examiner. MAX L. LEVY, Examiner. 

1. A THERMOSTATIC ALARM ASSEMBLY COMPRISING, ANCHOR MEANS, FIXED CONTACT MEANS SPACED FROM SAID ANCHOR MEANS AND THERMAL DEFLECTING COIL MENS INCLUDING A COIL SECTION OPERATIVELY CONNECTED TO THE ANCHOR MEANS FOR UNCOILING IN RESPONSE TO AN INCREASE IN THE AMBIENT TEMPERATURE OF ITS SURROUNDING MEDIUM, A REVERSELY COILED SECTION RESPONSIVE TO AN INCREASE IN THE AMBIENT TEMPERATURE OF ITS SURROUNDING MEDIUM FOR COILING SIMULTANEOUSLY WITH SAID UNCOILING OF SAID COIL SECTION, MEANS INTERCONNECTING SAID COIL SECTIONS FOR SIMULTANEOUS COILING AND UNCOILING WITH RESPECT TO MOVABLE COIL CENTERS DISPOSED BETWEEN SAID COIL SECTIONS AND MOVABLE CONTACT MEANS OPERATIVELY CONNECTED TO SAID REVERSELY COILED SECTION FOR DISPLACEMENT BY THE REVERSELY COILED SECTION IN A CONTACT PRESSURE DIRECTION FOR POSITION CONTACT ENGAGEMENT, AND A CONTACT WIPING DIRECTION FOR SURFACE CLEANING OF SAID FIXED CONTACT MEANS. 